Process for preparing fertilizers



Patented Mar. 5, 1 929.

UNITED STATES COLOGNE, G.

PATENT OFFICE.

mm. coriocnm' 13300388 :03 rmaranmc mm Ho Drawing. Application filedJune 11, 1925, Serial 10. $8,549, and in Germany June 5; 1m

to convert the tri-calcium phosphate in the 1 phosphorites into thephosphoric acid combination-with a higher percentage of lime, for

' instance n the form of a tetra compound'or .combination such as isa$umed to exist in Thomas slag. According to the known process ofMathesius t here isadded to the phosphorites such quantities of lime andsilicie acid that the combination 5CaO. P O .SiO,

is produced. In many cases there is added according to the knownprocesses an addition of alkali compounds as a flux medium, where- .by,in addition tothe carbonates, mention is also made of the sulphates andchlorites of the alkalies.

Now whereas processes have been successfully carried out with the use ofalkali car bonates or silicates, other alkali-salts, as for instance,the far cheaper alkali sulphates have found no practical application,This is due to the fact that when using alkali sulphates, especially ofthe potash compounds, under the same conditions as laid down for the useofthe' carbonates or silicates, with a completely insuflicient yieldeasier soluble hosphoric acid' very considerable losses of occur due toevaporation. Apart from the material loss,

- especially when using the valuable potash 4o salts, the lining orlagging of the kilns or furnaces isrstrongly' attacked by the alkallvapour and sufiers an unusual degree of wear as carbonate incontradistinction tothe other known processes participates directly inthe formation of an calcium phosphate in such a manner that by theaddition of the silicic acid there is bound from the tri-caLciumphosphate a molecule of CaO in the form of calciumorthosilicate, andthe alkali metal oxide takes its place under directbinding with thephosphoric acid, presumably in the manner of the following equationHence in contradistinction to the process that has hitherto become knownthere occurs no formation of a phosphoric acid combination rich in lime,but the lime phosphoric acid combination occurring in the phosphoriteshas still lime withdrawn it under formation of an alkali calciumphosphate,

Also according to this reaction,- however,

it is not possible, though observing the known conditions, to replacethe carbonate by other alkali salts. The existing ph horic acid isonlyconverted to the extent 0 hardly 70% into aform soluble in citrateor citricacid and, consequently, considerable losses in alkali occur. i

Now it has been found that itlis possible to completely convert thephosphoric acid into a form entirely soluble in citrate or citric acidand to avoid the loses of alkali caused by evaporation, be so calculatedmetal oxide there is used at least one molecule of silicic acid and atthe same time the glowing or heating proces is carried out in'the" ifthe addition of silicic acid that to one molecule alkali peresenoe ofsteam, and if, furthermore, care taken'that the silicic acid used bebound as orthosilicate 2CaO.SiO,, if n with the addition of .or thelike; v Under these conditions at a temperature of 9001000(a Be alkalialts is o tained, without any eva ration of these'taking place. The

and tear. 7

Moreover all these processes work without takes place, for exam 10 withtheuse' of any reco ble chemical reaction,inanuretasm'um sul hate, problydnsuch at 1y empirical manner and yield products with firstlysulphate andsilicic acid react as folabout 15% citrate or citric acidsoluble phoslows: 1 Phoricacid v I V m+8 0:-m+n

A further process has'also been described -The meta silicate thus formedis 5 to which the addition of alkali does then converted without any intamnot serve as a flux medium but the alkali used perature being 11 withthe triple basic phosphoric acid lime, ander iorlnathm of tfectdecomposition of the k .does not potash calcium phosphate, K CaAPOJ Whencompleted the process may be assumed to be as follows:

C33( A)2 K2 i 'FSlOz: 4- CQC'O3= 1 momm (26110510 so, cos. As thisequation shows, by mixture ct phos phorite with alkali salts,silicic'acid and allialine earth compounds such as carbonic acid lime,caustic lime, carbonate or magnesium, oxide of magnesium, etc. under theconditions as given in the above equation, whilst the silicic acidpresent in the raw phosphate per se and the alkaline earth combinationsnot 1 bound in phosphate must be talren into consideration, on glowingor heating in the presence of steam at temperatures of 1000", a loosesintered product which contains the phosphoric acid used in a formsoluble in citrate is obtained, 1 V.

N ow it use he made of potassium sulphate, there is then obtained afertilizer of excellent nature or composition; as the whole of itsphosphoric acid is present in a citrate soluble form and the lime isnot, as with the otherwise usual potash fertilizers, bound in acidsprejudicial to the plants.

It is remarkable and astonishing thatit a suitable product, also whenall other 0011- ditions correspondingto the above mentioned reactionequation are complied with. An increase of temperature above 1000?isalso of no use in this case as then an evaporation supervenes of thealkali combination in an unaltered form. If on carrying out the processthe material toibe burnt is heated direct by a steam generating flame,for example by water gas heating, then it is according to the hydrogenpercentage of the heating gas either entirely unnecessary to conductfurther quantities of steam over the material to the .glowing or heatingcording to the present titative yields 1 are obtained.

[ out that the products obtained to be burnt, or else only to supplysmall complementary quantitie The present invention shows a notabletechnical and economic elfect inthe production of phosphoric acidfertilizers according process. From ma be pointed ave an e8-traordinarily high precenta e of phosphoric acid, and up to 30% citricsoluble phosphoric acid that consequently in comparison -with otherprocesses the masses to be moved and heated in course ofmanufacture,represent the smallest possible-quantities, and that soprocess almostquanthe technical point of view it From the economic point of view an,unusually good effect is obtained, due to the Tfact'that low gradehosphorites, containing muchsilicic' acidpw 'ch for example would -"begofno for the manufacture of superphosphate, can be: used with advantagewhilst cheaper materials, as for instancafal prove successful to obtainby glowmg or heatingwithout the presence of steam aluminium oxide andiron oxide existing in the natural phosphorites. v r

The acid gases generated during the car. rymg out of the process can beturned to account according to the known process.

Working example.

100 partsotaNorth-Atrican raw phosphate with 39.7% P 0 47.0% @210 boundin phosphoric acid, 5,61% UaO not bound in phosphoric acid and 0,56%Sit), were thoroughly mixed with parts ct technical potassium sulphatewith a content of 448% K 0, 15,5 parts quartz and 20 parts lime stone,The mixture was glowed or heated at a temperature of about 1000 steambeing guided over it. lhe heated product contained: 27.46% totalphosphoric acid 26.61% citrate soluble phosphoric acid (soluble inammoniacal ammoncitrate solujtion according to Petermann) that is tosay.

97% recovery of the total phosphoric acid.

18.47% potash. 1

ly driven out of the product, and the material separatedofi' only. stillcontained 0.48%

mm Patent of the United States is:

'1; A process for preparing .fertilizers, comprising forming a mixtureof mineral phosphorites which mixture contains for "every molecule of P0 about one molecule of alkali metal oxide in the form of its salts andat least one molecule of silica, and for every molecule of silica suchquantities of lime that in addition to an alkali calcium phosphate,calcium orthosilicate may be formed, and subjecting said mixture to aheating at a temperatureof at least 900 C. in the presence of steam. a a

2. A process for preparing fertilizers, comprising forming a mixture ofmineral ica, which mixture contains forevei'fy cule of P 0 about onemolecule 0 metal oxide in'the form of its salts a molealkali at leastonemolecule of .silica and for every temperature of at least 900 C; in thepres" ence of steam. g I 3. A process for preparing ifertllizcrs,comprising form ng a mixture of mlneral every molecule of P 0, about onemolecule of alkali metal oxide in the form of its salts What we claimand desire to secure by Let- The sulphuric acid was practicallyentirephosphorites which are rich in lime and silphosphorite's whichmixture contains for a and at least one molecula-ofsuch on equiva- 130,

lent of silica which is tam bindCaO and for every molecule of such anequivalent of silica such uantities of CaO that in addition to an alkaicalcium phosphate a calcium compound corresponding to calciumorthosilicate may be formed, and subjecting said mixture to a heating ata temperature of at least 900C. in the presence of steam.

4. A process for preparing fertilizers, comprising forming a mixture ofmineral phosphorites which mixture contains for every molecule of Pabout one molecule of alkali metal oxide in the form of its salts andatleast one molecule of silica and of such equivalents of silica whichare able to bind (1:10 and for every molecule of silica and itsequivalents such quantities of 0:10 that in addition to analkali-calcium phosphate, calcium orthosilicate and other calciumcompounds corresponding to calcium orthosilicate may be formed, andsubjecting said mixmm to a heating at a temperature of at least 900 C.in the presence of steam.

5. A process for preparing fertilizers, comprising forming a mixture ofmineral phosphorites which mixture contains for every molecule of P 0about one molecule of alkali metal oxide in the form of its sulphate andat least one molecule of silica and for every molecule of silica suchquantities of lime that in addition to an alkali calcium phosphatecalcium orthosilicate may be formed and subjecting said mixture to aheating at a temperature of at least 900 C. in the presence of steam.

DR. FRITZ ROTHE. Dn. HANS BRENEK.

